<template>
  <div class="todo-footer">
    <label>
      <!-- 这里既要获得值，又要修改值，所以使用双向绑定 -->
      <input type="checkbox" v-model="checkAll" />
    </label>
    <span> 
      <span>已完成{{finishAll}}</span> 
      / 全部{{todoList.length}}
      </span>
    <button class="btn btn-danger" @click='deleteAll' >清除已完成任务</button>
  </div>
</template>

<script>
export default {
    name:'Footer',
    props:['todoList','AllChecked','deleteAll'],
    // 计算属性
    computed:{
      finishAll(){
        //返回一个累加的数值,c是每一项，c.done时true时，才加1
        return this.todoList.reduce((p,c)=> (c.done? p+1 : p),0)
      },

      checkAll:{
        set(value){
          this.AllChecked(value)
        },
        get(){
          //every判断条件是item全部为true时，就返回true，如果有一个false就是false
         return this.todoList.every((item)=> item.done) && this.todoList.length !== 0
        }
      }
    }

};
</script>

<style scoped>
/*footer*/
.todo-footer {
  height: 40px;
  line-height: 40px;
  padding-left: 6px;
  margin-top: 5px;
}

.todo-footer label {
  display: inline-block;
  margin-right: 20px;
  cursor: pointer;
}

.todo-footer label input {
  position: relative;
  top: -1px;
  vertical-align: middle;
  margin-right: 5px;
}

.todo-footer button {
  float: right;
  margin-top: 5px;
}
</style>